Correct extended error for binary_to_term/2

When `binary_to_term/2` failed with a `badarg` exception, the extended error
information would always blame the second argument even if the error was
in the first argument:

    1> binary_to_term(<<"">>, []).
    ** exception error: bad argument
         in function  binary_to_term/2
            called as binary_to_term(<<>>,[])
            *** argument 2: invalid option in list
    2> binary_to_term(<<131,100,0,10,97,95,110,101,119,95,97,116,111,109>>, [safe]).
    ** exception error: bad argument
         in function  binary_to_term/2
            called as binary_to_term(<<131,100,0,10,97,95,110,101,119,95,97,116,111,109>>,
                                     [safe])
            *** argument 2: invalid option in list

Correct the extended error information like this:

    1> binary_to_term(<<"">>, []).
    ** exception error: bad argument
         in function  binary_to_term/2
            called as binary_to_term(<<>>,[])
            *** argument 1: invalid external representation of a term
    2> binary_to_term(<<131,100,0,10,97,95,110,101,119,95,97,116,111,109>>, [safe]).
    ** exception error: bad argument
         in function  binary_to_term/2
            called as binary_to_term(<<131,100,0,10,97,95,110,101,119,95,97,116,111,109>>,
                                     [safe])
            *** argument 1: invalid or unsafe external representation of a term

Closes #5171.

3 files changed, 32 insertions, 6 deletions

diff --git a/erts/emulator/beam/external.c b/erts/emulator/beam/external.c
index 6bfd9fa825..efb315842a 100644
--- a/erts/emulator/beam/external.c
+++ b/erts/emulator/beam/external.c
@@ -2101,7 +2101,8 @@ BIF_RETTYPE binary_to_term_2(BIF_ALIST_2)
     return binary_to_term_int(BIF_P, BIF_ARG_1, &ctx);
 
 error:
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = am_badopt;
+    BIF_ERROR(BIF_P, BADARG | EXF_HAS_EXT_INFO);
 }
 
 Eterm
diff --git a/erts/emulator/test/exception_SUITE.erl b/erts/emulator/test/exception_SUITE.erl
index 18a5dda447..746993bf34 100644
--- a/erts/emulator/test/exception_SUITE.erl
+++ b/erts/emulator/test/exception_SUITE.erl
@@ -680,7 +680,7 @@ do_error_3(Reason, Args, Options) ->
 
 error_info(_Config) ->
     DeadProcess = dead_process(),
-    NewAtom = non_existing_atom(),
+    {NewAtom,NewAtomExt} = non_existing_atom(),
     Eons = 1 bsl 50,
 
     %% We'll need an incorrect memory type for erlang:memory/1. We want to test an
@@ -767,9 +767,14 @@ error_info(_Config) ->
          {binary_to_list, [<<1,2,3>>, 4, 5]},
 
          {binary_to_term, [abc]},
-         {binary_to_term, [<<"abc">>]},
+         {binary_to_term, [<<"bad">>]},
+
          {binary_to_term, [term_to_binary(a), abc]},
          {binary_to_term, [<<"bad">>, abc]},
+         {binary_to_term, [<<"bad">>, [bad]]},
+         {binary_to_term, [<<"bad">>, []]},
+         {binary_to_term, [<<"bad">>, [safe]]},
+         {binary_to_term, [NewAtomExt, [safe]]},
 
          {bit_size, [abc]},
          {bitstring_to_list, [abc]},
@@ -1322,7 +1327,9 @@ non_existing_atom(Atom) ->
             non_existing_atom([Char|Atom])
     catch
         error:badarg ->
-            Atom
+            AtomBin = list_to_binary(Atom),
+            AtomExt = <<131,100,(byte_size(AtomBin)):16,AtomBin/binary>>,
+            {Atom,AtomExt}
     end.
 
 do_error_info(L0) ->
diff --git a/lib/kernel/src/erl_erts_errors.erl b/lib/kernel/src/erl_erts_errors.erl
index 0b2b89ceac..8b0768ac80 100644
--- a/lib/kernel/src/erl_erts_errors.erl
+++ b/lib/kernel/src/erl_erts_errors.erl
@@ -264,9 +264,25 @@ format_erlang_error(binary_to_list, [Bin,Start,Stop], _) ->
     end;
 format_erlang_error(binary_to_term, [Bin], _) ->
     [must_be_binary(Bin, bad_ext_term)];
-format_erlang_error(binary_to_term, [Bin,Options], _) ->
+format_erlang_error(binary_to_term, [Bin,Options], Cause) ->
     Arg1 = must_be_binary(Bin),
-    [Arg1,maybe_option_list_error(Options, Arg1)];
+    Arg2 = case Cause of
+               badopt ->
+                   must_be_list(Options, bad_option);
+               _ ->
+                   []
+           end,
+    case {Arg1,Arg2} of
+        {[],[]} ->
+            case lists:member(safe, Options) of
+                true ->
+                    [bad_or_unsafe_ext_term];
+                false ->
+                    [bad_ext_term]
+            end;
+        {_,_} ->
+            [Arg1,Arg2]
+    end;
 format_erlang_error(bitstring_to_list, [_], _) ->
     [not_bitstring];
 format_erlang_error(bump_reductions, [Int], _) ->
@@ -1290,6 +1306,8 @@ expand_error(bad_encode_option) ->
     <<"not one of the atoms: latin1, utf8, or unicode">>;
 expand_error(bad_ext_term) ->
     <<"invalid external representation of a term">>;
+expand_error(bad_or_unsafe_ext_term) ->
+    <<"invalid or unsafe external representation of a term">>;
 expand_error(bad_isdst) ->
     <<"not 'true', 'false', or 'undefined'">>;
 expand_error(bad_localtime) ->